Ahu Ahu Road Swell Statistics, July: All Swell – Any Wind
This picture illustrates the variation of swells directed at Ahu Ahu Road through a typical July and is based upon 2480 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about Ahu Ahu Road, and at Ahu Ahu Road the best grid node is 17 km away (11 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing without direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These occurred only 14% of the time. Green and yellow show increasing swell sizes and red represents largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was W, whereas the the most common wind blows from the SSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Ahu Ahu Road and away from the coast. We combine these with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Ahu Ahu Road, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average July, swells large enough to cause good for surfing waves at Ahu Ahu Road run for about 86% of the time.
IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.